Numerous materials are packaged in flexible containers, such as flexible pouch-like containers. Such pouches may be formed from pairs of webs which are heat sealed to one another, or the pouch may be formed of a single web which is folded, with the side seams and top seam, and optionally the folded bottom edge, being heat sealed. Such pouch-like containers may be fabricated from thermoplastic resins or laminates including inner heat-sealable layers fabricated from thermoplastic resins. Thus, pouches are commonly formed from a pair of lamina in which each lamina comprises an outer layer of a plastics resin film, a central barrier layer of a metal foil, such as aluminum foil, and an inner layer of a heat-sealable thermoplastic resin film or from folded webs of these sheet materials.
In filling and sealing pouches with foodstuffs and the like, contamination of the top edge region of the pouch, which is the area where the final seal is to be formed, is a continuing problem. Quite often, solid food particles will cling to the walls of the pouch in the edge region where this heat seal is to be located. This contamination requires that the region to be heat sealed be cleaned of food particles prior to sealing, since these particles will interfere with the heat sealing operation, causing gaps, blisters, blemishes or other defects in the heat seal and possible failure in the seal. Such cleaning has in the past been accomplished by means of pressurized steam.
In order to partially remove air from such containers prior to sealing thereof, steam has in the past been injected into the containers prior to sealing. It has, heretofore, been the practice to either inject steam into a container for air removal purposes or to direct pressurized steam for cleaning purposes. It has been unknown to simultaneously treat flexible containers by injecting steam and directing pressurized steam to accomplish both of these purposes. It is thus a primary aspect of the present invention to enable these two results to be accomplished at a single forming station.
It has also been found that, with such materials as gravy and other liquid and semi-liquid foodstuffs, these materials can accumulate on the outside of the container, especially at the top edge region of the container. This interferes with the heat sealing operation in that the foodstuffs on the outside of the container quickly transfer to the heated bars which are used for sealing of the containers, resulting in reduced heat transfer rates for the heated bars and thus increased down time for cleaning and/or replacement of protective covers for these heated bars. It is thus an additional objective of the present invention to cleanse both the inner and outer edge of the container prior to heat sealing thereof.